Immunofluorescence is routinely employed in testing human serum for the presence of anti-treponemal antibodies associated with syphilis. The immunofluorescent antibody technique consists of two antigen--antibody reactions. The first reaction takes place between anti-treponemal antibody contained in the serum sample and specific antigen localized in a particular substrate. The second reaction is between the anti-treponemal antibody/antigen complex and antihuman immunoglobin (Ig) antibody that has been tagged with a fluorescent label. After the second reaction, the substrate is examined for fluorescence using the fluorescent microscope. In positive samples, the patterns of fluorescence are used as indicators for additional tests.
In spite of its accuracy and ease of use, the immunofluorescent antibody technique has one major disadvantage. It does not allow for quick screening of a number of serum samples since each sample must be individually studied under a fluorescent microscope to ascertain whether the serum is positive or negative. Since the majority of sera routinely tested are negative for anti-treponemal antibody, the advantages of a method which would eliminate microscopic examination of negative sera are obvious. Such a method would be less labor intensive and therefore less expensive.
It is an object of the present invention to provide a fast and accurate method of screening a large number of serum samples for anti-treponemal antibody, which, when present, can be further confirmed by fluorescent microscopy.